We have developed a system to simplify the study of human cell surface structures by procedures which permit study of antigens due to individual chromosomes. A human-Chinese hamster, somatic cell hybrid, which contains chromosome 11 as its only human chromosome has been produced. This hybrid, which expresses human cell surface antigens, has been employed as a model system to study these components using a combined immunological, biochemical, and genetic approach. We have developed a deletion clone panel of chromosome 11, which has enabled us to conduct a variety of regional mapping studies including development of a new method using a low-repeat human DNA sequence. The production of monoclonal antibodies has allowed us to further characterize these antigens and to identify new antigens encoded by chromosome 11. We have recently carried out similar studies using hybrids that retain only human chromosomes 3 and 21. Deletion panels are being developed for these chromosomes and have been used for regional mapping. Studies of this kind should make possible rapid and definitive identification of a large variety of human cell surface antigens which may influence malignant behavior of human cells. The chromosomal location and biochemical identity of such genetic determinants may help elucidate genetic relationships of antigens involved in malignant response. (CS)